Effect of Prosthetic Rehabilitation on Airway Space in Edentulous Patients with Obstructive Sleep Apnea- a Preliminary Observational Study

Statement of the Problem: The common causes of obstructive sleep apnea (OSA) are identified as anatomic and/or functional abnormality in the oral cavity, oropharynx, velopharynx, and hypopharynx leading to compromised airway space and increased collapsibility. Purpose: This study was conducted to evaluate the effect of implant-supported mandibular complete denture in improving the airway space among completely edentulous patients with OSA and compare it with conventional complete denture. Materials and Method: In this observational study, completely edentulous individuals were screened with snoring, tiredness, observed apnea, high blood pressure, body mass index, age, neck circumference, and gender (STOP-Bang) questionnaire to evaluate the incidence of OSA. Ten mild-moderate patients were included as study participants. Lateral cephalograms (L1) made at the edentulous state was considered baseline. They were rehabilitated with complete denture prosthesis. One week after denture insertion, two implants were placed in the edentulous mandibular arch. Delayed loading protocol was followed. Lateral cephalogram (L2) was made 6 months after complete denture insertion and 6 months after implant-supported prosthesis (L3). Cephalometric tracings were used to evaluate change in upper airway space (UAS), middle airway space (MAS), and lower airway space (LAS). Repeated measures ANOVA was used to evaluate statistical significance in the airway measurements made at the three intervals. Post hoc Tukey HSD and Bonferroni test were used to assess if the differences obtained were truly significant. Results: Statistical analysis revealed significant differences in UAS, MAS and LAS between L1, L2 and L3 (p< 0.05). Post hoc Tukey HSD indicated that UAS increased significantly at all three intervals followed by LAS and MAS respectively (α=.05). Post hoc Bon-ferroni test indicated that implant-supported mandibular complete dentures had a significant improvement in airway space when compared to conventional complete dentures (α=.05). Conclusion: Implant-supported mandibular complete denture could be effective in edentulous patients with mild-moderate OSA.


Introduction
The common causes of obstructive sleep apnea (OSA) are identified as anatomic and/or functional abnormali-ty in the oral cavity, oropharynx, velopharynx, and hypopharynx leading to compromised airway space and increased collapsibility [1].Several studies have Evaluation of airway space after implant-supported complete dentures Krishnamurthy P, et al 10.30476/dentjods.2022.95716.1886383 proved that edentulism can be considered as one of the exacerbating factors that could worsen OSA [1][2].
Complete edentulism causes changes in the postural position of mandible, muscle tone, tongue posture and vertical dimension, thereby affecting airway dimensions.These morphological changes cause challenges in treating such edentulous sleep apneic patients [2][3][4]; however, it is underdiagnosed and not characterized in elderly edentulous.Diagnosing and treating OSA is important to improve quality of life, reduce morbidity, and mortality [5].Alternatives to the standard method of using polysomnography to diagnose OSA are becoming increasingly popular due to its expense and/or limited availability [6].Questionnaires are appropriate tools for quick chair side prediction [7].Though computed tomography and magnetic resonance imaging have been regarded as the best method of anatomic evaluation, they require more technical expertise, and expenses.In this regard, cephalometric analysis can play a significant role in identifying patients at risk for OSA [8].Numerous cephalometric parameters have been associated with its occurrence and it is a simple, safe, and economic method to depict the relevant anatomy of the airway spaces [8].Oral appliances like mandibular repositioning device and tongue retainers gained recognition in treating dentulous sleep apneic patients.However, in edentulous patients the retention is not enough to accommodate the appliances intraorally [9].Complete dentures have been used in edentulous sleep apneic patients to increase the airway space and reduce apneic episodes [6].Owing to short follow up, the effects of wearing dentures is inconclusive [10].Moreover, a lack of stability and retention together with residual bone resorption would decrease the chewing ability in patients wearing conventional complete dentures.Implant-supported dentures provide greater retention, stability, and quality of life for edentulous patients [11].Considering the benefits conferred by implant-supported complete dentures, the present study aimed to evaluate the impact of implant-supported mandibular complete denture in improving airway spaces in completely edentulous individuals with mild-moderate OSA and compared it with conventional complete denture prosthesis.The null hypothesis stated that there was no difference in airway space dimensions among mild-moderate sleep apneic edentulous patients rehabilitated with complete dentures and implant-supported mandibular complete denture.informed consent was obtained.They were screened using the snoring, tiredness, observed apnea, high blood pressure, body mass index, age, neck circumference, and gender (STOP-Bang) questionnaire, which is specifically developed to meet the need for a reliable, concise, and easy-to-use screening tool [9,12].It consists of eight dichotomous (yes/no) questions related to the clinical features of OSA.The patients were able to respond to most of the questions.When they were not aware of their behaviour during sleep, spouse or children answered those questions.For each question, answering "yes" scores 1, a "no" response scores 0, and the total score ranges from 0 to 8. Patients with a STOP-Bang score of 0 to 2 can be classified as low risk for moderate to severe OSA, scores in the midrange (3 or 4) as moderate risk for moderate to severe OSA, whereas those with a score of 5 to 8 can be classified as high risk for moderate to severe OSA (Table 1) [12].Adopting 95% power in calculating sample size (G*Power 3.1.9.2) and  Cephalometric variables depicting the upper airway space (UAS), middle airway space (MAS), and lower airway space (LAS) were traced by the principal investigator following the standard procedure.UAS was defined as the distance between the pterygomaxillary and upper pharyngeal wall (pm-UPW), MAS was the distance between the tip of the uvula and middle pharyngeal wall (U-MPW), and LAS was the distance between the vallecula and the lower pharyngeal wall (V-LPW) (Figure 1).The dimensions were measured in millime-     UAS was statistically more significant followed by LAS and MAS (α=.05).Intergroup Post hocanalysis using Bonferroni test indicated that the difference in the UAS and MAS obtained at L2 and L3 was truly significant (α =.05) when compared with L1 as seen in Table 7.However, the differences in LAS were truly significant only at L3.

Complete edentulism results in reduction of lower facial
. These changes along with abnormal tongue position predispose edentulous patients to OSA.Although an overnight polysomnography is the gold standard diagnostic test, it is time consuming, labour-intensive, expensive and requires the expertise of sleep medicine specialists [5,[16][17].Thus, a simple chairside screening tool is required to assist in identification.The STOP-Bang questionnaire has demonstrated high sensitivity in detection across various populations [9].In this study, it has assisted in identifying patients with risk for OSA.
Oral appliances were found to be more satisfactory for mild to moderate OSA patients and contraindicated in patients categorised with severe OSA [17].Complete dentures have been used as an oral appliance for patients with mild-moderate OSA [18][19].They improved airway space through positional changes in mandible, tongue, and soft tissue.However, the results of studies assessing the effectiveness of complete dentures on airway space done in the past were inconclusive [18,20].
This study aimed to evaluate the effect of complete dentures on the airway space for a period of six months and the improvement in airway space with implantsupported complete dentures was assessed in the same study population.Both male and female study participants had worn complete dentures fabricated using conventional method and routine materials thus providing a homogenous and representative sample [18].Airway space dimensions were measured on lateral cephalograms by two investigators.The cephalometric method, despite being a static two-dimensional method to evaluate anatomical structures of the head and neck, has been useful in assessing airway space.Repeated measures ANOVA revealed a statistically significant increase in the UAS, MAS, and LAS dimensions in L2 made six months after insertion of complete denture when compared with dimensions in L1 made at completely edentulous state with a p< 0.05 (Tables 2-4).We speculate that the increase in airway dimensions could have occurred due to the positional changes of the mandible.
Complete dentures help re-establish maxilla-mandibular relationship.This in turn helps in restoring the tongue to its normal position and prevents blocking of airways.
Additionally, the tonicity and function of the surrounding soft tissues are restored, which helps reduce pharyngeal collapsibility [18].The results of the present study were in correlation with the findings of Gao et al. [21], who confirmed the positive effect of complete dentures on enlarging upper airway.Erovigni et al. [22] also stated that complete dentures increased the diameters of the velopharynx, oropharynx in the sagittal plane as well as at the uvula level.
Although complete dentures are the first option for rehabilitating edentulous patients, the mandibular complete denture lacks sufficient retention and stability.
This affects patient compliance in wearing complete dentures, deteriorating its positive influence on airway space.Implant-supported mandibular denture had evolved as a viable option for edentulous patients with improved retention and quality of life [11].In this study, mandibular complete dentures of the participants were converted into an implant-supported denture.Lateral cephalograms (L3) obtained six months after implantsupported prosthesis assessed the effect of implantsupported mandibular complete denture on the airway space.The values obtained with L3 were compared with the values obtained at L1 and L2.Post Hoc Bonferroni test indicated that the differences in UAS, MAS and LAS were found to be statistically significant after wearing implant-supported mandibular complete dentures (L3) when compared with conventional complete dentures (L2) and at edentulous state (L1) at p< 0.05 (Table 7).This increase, when compared to conventional complete dentures, could have been due to better retention, stability, patient comfort, and compliance, which in turn contributes to improved muscle tone and function [23].Post Hoc Tukey HSD assessed the difference in the airway dimensions at the three-time intervals between both complete denture and implant-supported mandibular denture.It indicated a significant increase in UAS followed by LAS and MAS with implantsupported mandibular complete denture (L3) (Table 6).
Upper airway collapse has been found to be more common in patients with OSA [2].Thus, the results of this study indicate that implant-supported dentures itself can act as an oral appliance to increase airway space in edentulous sleep apneic patients.Hoekema et al. [24] identified mandibular advancement device, which was retained with a single implant, to be effective in edentulous sleep apneic patients.Moreover, the quality of life and sleep characteristics substantially improved with prosthetic rehabilitation in completely edentulous patients who had mild-moderate OSA.
In this study, the edentulous population benefitted

Conclusion
Within the limitations of this study, the following conclusions were drawn.Implant-supported mandibular complete dentures improved airway space dimensions when compared with conventional complete dentures in edentulous patients with mild-moderate OSA at the end of twelve months.Among the three airway dimensions, the increase in UAS was statistically significant when compared to MAS and LAS for both modes of rehabilitation indicating a positive influence of complete dentures on airway space.
Formal Ethical approval was obtained from the Institutional Ethics Committee of Sri Ramachandra Institute of Higher Education and Research (SRIHER, DU) (REF-ERENCE NO: CSP/19/NOV/81/420).Patients with completely edentulous arches who visited the Department of Prosthodontics were explained about the study and an regarding the study of Milosevic et al.[13], ten patients aged between 50-65 years, who were first time denture wearers with well-formed residual ridges in Class 1 relation and characterized into low-mode-rate risk category were included as study participants.Patients with history of any metabolic syndrome, surgery of tongue, palate or upper airways, skeletal l class III relationship, grossly resorbed residual alveolar ridges, and musculoskeletal disorders were excluded from the study.Standardised lateral cephalograms (X-ray device-CARESTR-EAM) were made for all the study participants at edentulous state and was considered baseline (L1).The participants were further screened using lateral cephalograms to eliminate nasal obstruction or pharyngeal tumours.

Figure 1 :
Figure 1: Cephalometric variables depicting Airway space Evaluation of airway space after implant-supported complete dentures Krishnamurthy P, et al 10.30476/dentjods.2022.95716.1886387 from both complete dentures and implant-supported mandibular complete dentures.Hence, the follow-up period evaluated the impact of both the modes of prosthetic rehabilitation on the airway space.No other study has assessed the effect of implant-supported mandibular complete dentures on the airway space dimension among edentulous patients.While this observational study included ten participants for evaluation, a randomized controlled trial with a larger sample size can help in validating the results.The cephalometric tool used in this study evaluated the antero-posterior diameter of the airway.Subsequently, a three-dimensional evaluation with a longer follow-up in edentulous individuals might assist in drawing conclusions that are more definitive.

Table 6 .
However, the difference in

Table 2 :
Assessment of upper airway space dimensions (UAS) in mm

Table 3 :
Assessment of middle airway space dimensions (MAS) in mm

Table 4 :
Assessment of lower airway space dimensions (LAS) in mm